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Discussion Starter #1
I see where I can 'SEARCH THE COMMUNITY' - but that seems to search all forums. How do I search ONLY the GRAND MARQUIS FORUM?

I want to search on 'battery light' and 'alternator'.

Thanks,
Matt
 

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I dont use the desktop site so Im not sure but whats the issue that youre trying to look up?


Sent from my iPhone using Tapatalk
 

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I dont think the search on here is that sophisticated to searching .

P.s

Your other post deleted as double posting does not help anyone in answering .
 

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Discussion Starter #4
I dont think the search on here is that sophisticated to searching .

P.s

Your other post deleted as double posting does not help anyone in answering .
Thanks for letting me know. I was wondering where my post in THE PUB went.

I posted there as I thought my question was more general in nature. And, also because I did not see my post show up in this GRAND MARQUIS section after I posted here.
 

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Discussion Starter #5
I dont use the desktop site so Im not sure but whats the issue that youre trying to look up?


Sent from my iPhone using Tapatalk
Last night driving home, my battery light came on in the dash. I also noticed my headlight were dimmer.

When I got home, I put a meter on my battery, and the meter only read around 11.6 volts.

I started looking online for testing procedure on an alternator, and found one that said to start the car, and look for an increase in voltage at the battery terminals of at least 0.5 volts over my battery voltage, and ideally around 14.2 to 14.7 volts - which would indicate the alternator was charging the battery.

I started the car but I still only saw around 11.6 volts at the battery terminals.

I think my alternator might be bad, but I wanted to search this forum for testing and diagnosis that others, with a Marquis, have done, to confirm that it's not my battery that has gone bad, but is the alternator, before i pull the alternator off and replace it with a rebuilt one from Autozone. That is what I think I am going to do today.
 

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Those readings indicate your alternator is not charging and you are only getting the battery voltage which also is low due to non charge .You dont say what year or size of engine but this should help you ,

https://http://shop.muthco.com/content/pdf/install/21000860.pdftroubleshootmyvehicle.com/ford/4.6L-5.4L/how-to-test-the-alternator-1
 

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Discussion Starter #7
Those readings indicate your alternator is not charging and you are only getting the battery voltage which also is low due to non charge .You dont say what year or size of engine but this should help you ,

https://http://shop.muthco.com/content/pdf/install/21000860.pdftroubleshootmyvehicle.com/ford/4.6L-5.4L/how-to-test-the-alternator-1
Thanks. But that link is not working for me...

My car is a 1997 Grand Marquis. 4.6L V8 engine.

I had autozone test the alternator. It failed all 3 tests, 1)rectifiers, 2)diodes, and 3) I cant remember.

So, I bought a new alternator from Autozone (new, not reman). It is showing me 13.3v with the car idling. I can get it up to 13.7v at about 2000 rpm, and up to 13.8v if i go above 2000 rpm. Is that too low?

Most thing I am finding with google are saying a good alternator will put out around 14.3v to 15v.
 

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Discussion Starter #8
So, I drove the car for about 30 minutes with the new alternator installed.

Then I tested the voltage output again.

This time I am getting 14.2v across the battery terminals with the car running. Still not getting the 14.7v I keep seeing as the ideal voltage. But, a good jump from the 13.2v I was seeing immediately after the alternator was installed.

I wonder if driving it at 55 mph for 30 minutes got the alternator spinning with less resistance, or something? And perhaps that is why the voltage reading bumped up to 14.2 volts?

I was going to return the new alternator for a 2nd new one, but now I'm not sure what to do? Any thoughts?
 

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Normal alternator output is between 13.5 to 14.5 volts. It all depends on the condition/state of the battery and the drain on the electrical system that's being used by the ignition, fuel pump, lights and accessories. As long as your drawing at least the minimum you're good to go.
 

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Discussion Starter #12
How long was the battery charged before? 14.2 isn't enough to worry about. Trickle charge it overnight and then run the test
Well, the battery was down to 11.6v when I first tested the new alternator charging voltage at 13.2v.

At the second test I had been driving for half an hour, so I imagine the battery was slightly higher charge, and the alternator charging rate was at 14.2v.

This morning the batter was 12.7v, or so, and the third reading was 14.5 on alternator chargin rate.

So, was it the battery getting more recharged that maybe caused the alt to charge higher?
 

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Discussion Starter #13
You dont need it now , but this should work .

Thank you. That is the information I needed. Since I am between 14 and 14.5 NOW - I think my new alternator is working correctly!.

thanks for that link. I am going to bookmark it for future reference! I that free?

BTW. Last night I was looking at the Mitchell online site, as well as the alldata Both are subscription. About $25/year, or $50 for 5 years. The Mitchell sight looked easier to nnavigate. I had used alldata one before, and although thorough, is harder to navigate. Anyone here recommend one over the other? Or maybe a different site?
 

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Never used Michelin , it was always Alldata in the service dept to supplement the dealer literature we had . You readings now seem fine , probably because the battery is now recovered . The link is free . Needing any more help , get back to us
 

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Discussion Starter #16
Never used Michelin , it was always Alldata in the service dept to supplement the dealer literature we had . You readings now seem fine , probably because the battery is now recovered . The link is free . Needing any more help , get back to us
THANKS. For all your help and feedback. This is a great forum,

...Matt
 
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